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T S Yen

Publications and source records attributed to T S Yen.

At least 19 recordsLinked to original sources
PubMed2001

CpG hypermethylation of the promoter region inactivates the estrogen receptor-beta gene in patients with prostate carcinoma.

BACKGROUND: The down-regulation of the estrogen receptor-beta (ERbeta) gene is associated with several malignancies, including prostate carcinoma. The purpose of the current study was to investigate the mechanisms of ERbeta inactivation through the analysis of CpG methylation of the promoter region of ERbeta gene. METHODS: ERbeta protein expression was examined by immunohistochemistry in 23 cases of human prostate carcinoma and 40 cases of benign prostatic hyperplasia (BPH). DNA was extracted from these tissues and processed for sodium bisulfite genomic sequencing. The percentage of methylation of CpG sites in the promoter region of ERbeta (-376 to -117), which contains 19 CpG sites, was determined from genomic sequencing data. The prostate carcinoma cell lines DU145 and ND1 were treated with the demethylating agent 5-AZAC and ERbeta mRNA expression was analyzed by reverse transcriptase-polymerase chain reaction. RESULTS: In BPH tissues, ERbeta protein expression was found mainly in epithelial cells. ERbeta protein expression was lacking in 83% of prostate carcinoma samples (19 of 23 samples) whereas all cases of BPH (40 of 40) demonstrated expression of ERbeta protein. The mechanism of inactivation of the ERbeta gene in prostate carcinoma was CpG methylation because the degree of methylation at all CpG sites within the promoter region between -376 and -117 was higher in prostate carcinoma samples compared with BPH tissues. Nine of 19 CpG sites within the promoter region of ERbeta displayed significant differences in methylation between prostate carcinoma and BPH samples. The prostate carcinoma cell lines appeared to lack ERbeta expression. However, 5-AZAC treatment restored ERbeta expression in those cell lines, suggesting that methylation inactivates the ERbeta gene in prostate carcinoma. CONCLUSIONS: The results of the current study demonstrate, for what we believe to be the first time, that the inactivation of the ERbeta gene in prostate carcinoma occurs through CpG methylation of the promoter region of this gene.

Azacitidine↗
PubMed2001

Synthesis of a novel hepatitis C virus protein by ribosomal frameshift.

Hepatitis C virus (HCV) is an important human pathogen that affects approximately 100 million people worldwide. Its RNA genome codes for a polyprotein, which is cleaved by viral and cellular proteases to produce at least 10 mature viral protein products. We report here the discovery of a novel HCV protein synthesized by ribosomal frameshift. This protein, which we named the F protein, is synthesized from the initiation codon of the polyprotein sequence followed by ribosomal frameshift into the -2/+1 reading frame. This ribosomal frameshift requires only codons 8-14 of the core protein-coding sequence, and the shift junction is located at or near codon 11. An F protein analog synthesized in vitro reacted with the sera of HCV patients but not with the sera of hepatitis B patients, indicating the expression of the F protein during natural HCV infection. This unexpected finding may open new avenues for the development of anti-HCV drugs.

Amino Acid Sequence↗
PubMed2001

Lupus-like kidney disease in mice deficient in the Src family tyrosine kinases Lyn and Fyn.

Systemic lupus erythematosus (SLE) is an autoimmune disease whose cause is poorly understood. Mice rendered deficient in specific genes have served as useful animal models in deciphering the genetic control of the disease [1]. We [2] and others [3, 4] previously demonstrated that mice deficient in the Src family tyrosine kinase Lyn developed a mild lupus-like disease with high survival rates. During the course of investigating the functional interaction of Src family kinases, we generated a mouse strain deficient in both Lyn and Fyn. The double-mutant mice died at relatively young ages and developed a severe lupus-like kidney disease. Unlike the double-mutant mice, single mutants deficient in either Lyn or Fyn lived longer and had distinct subsets of the symptoms found in the former. Lyn deficiency led to high levels of autoantibody production and glomerulonephritis, as previously reported [2--4], whereas loss of Fyn contributed to proteinuria by a B and T lymphocyte-independent mechanism. Our data suggest that the severe kidney disease in the double-mutant mice results from a combination of immunological and kidney-intrinsic defects. This new animal model may be informative about the causes of human SLE.

Animals↗
PubMed2001

Traumatic arteriogenic erectile dysfunction: a rat model.

We developed a rat model of traumatic arteriogenic erectile dysfunction (ED) for the study of vasculogenic ED. Bilateral ligation of the internal iliac artery was performed on 30 three-month old male Sprague-Dawley rats as an experimental group. The control group consisted of 12 rats which underwent dissection of the internal iliac artery without ligation. Before their euthanization at 3 days, 7 days, and 1 month (10 rats in the experimental group and four rats in the control group at each time point), erectile function was assessed by electrostimulation of the cavernous nerves. Penile tissues were collected for nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase staining, trichrome staining, electron microscopy and RT-PCR for transforming growth factor beta (TGF-beta1), insulin like growth factor-I (IGF-I) and fibroblast growth factors (FGF) mRNA expression. Electrostimulation of the cavernous nerves revealed a highly significant declining of the intracavernous pressure after 3 and 7 days. No significant recovery of erectile function was noted at 1 month. Histology showed degeneration of the dorsal nerve fibers in all experimental rats. There was little decrease in the bulk of intracavernous smooth muscle in the experimental rats euthanazed 7 and 30 days. NADPH diaphorase staining revealed a significant decrease in nitric oxide synthase (NOS) containing nerve fibers in the dorsal and intracavernosal nerves in all rats in the experimental group. Electron microscopy showed a variety of changes such as collapse of sinusoids, increased cell debris, fibroblast and myofibroblast loss, intracellular deposition of fat and collagen and fatty degeneration. RT-PCR revealed up-regulation of TGF-beta1 after 3 days but not after 7 days or 1 month. There is no significant difference in IGF-I or FGF expression between the experimental and control group. Bilateral ligation of internal iliac arteries produces a reliable animal model for traumatic arteriogenic ED. Further studies are needed to investigate the molecular mechanism of ED in this model.

Animals↗
PubMed2001

Role of polypyrimidine tract binding protein in the function of the hepatitis B virus posttranscriptional regulatory element.

The hepatitis B virus posttranscriptional regulatory element (PRE) is an RNA element that increases the expression of unspliced mRNAs, apparently by facilitating their export from the nucleus. We have identified a cellular protein that binds to the PRE as the polypyrimidine tract binding protein (PTB), which shuttles rapidly between the nucleus and the cytoplasm. Mutants of the PRE with mutations in PTB binding sites show markedly decreased activity, while cells that stably overexpress PTB show increased PRE-dependent gene expression. Export of PTB from the nucleus, like PRE function, is blocked by a mutant form of Ran binding protein 1 but not by leptomycin B. Therefore, PTB is important for PRE activity and appears to function as an export factor for PRE-containing mRNAs.

Base Sequence↗
PubMed2000

Activation of promoters for cellular lipogenic genes by hepatitis B virus large surface protein.

Hepatitis B virus large surface protein has the unusual property of accumulating in a particulate form within a preGolgi compartment, leading to marked proliferation of intracellular membranes. We show here that large surface protein activates the promoters for two lipogenic genes that code for farnesyl diphosphate synthase and fatty acid synthase. This activation is transduced, in part, by the transcription factor NF-Y. Although NF-Y is also necessary for the transcriptional induction of chaperone proteins residing in the endoplasmic reticulum by unfolded proteins, other inducers of chaperone synthesis do not activate the promoters for farnesyl diphosphate synthase and fatty acid synthase. Our results suggest the presence of a novel signaling pathway from the endoplasmic reticulum to the nucleus that causes the intracellular membrane proliferation seen in the hepatocytes of persons with accumulated large surface protein particles.

Alkyl and Aryl Transferases↗
PubMed2000

Diagnostic efficacy of (13)C-urea breath test for Helicobacter pylori infection in hemodialysis patients.

The noninvasive urea breath test (UBT) avoids the discomforts and risks of invasive endoscopic methods of Helicobacter pylori detection. This study investigated the diagnostic efficacy of carbon 13 ((13)C)-labeled UBT for H pylori detection in 70 patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD) and 70 dyspeptic controls without renal impairment. With H pylori infection defined as a positive result on either histological examination or culture of gastric biopsy specimen, we evaluated the reliability of the (13)C-UBT in detecting H pylori infection in both groups. To ascertain whether HD therapy affects the diagnostic efficacy of the UBT, the test was performed twice in patients with ESRD (before and after HD) at least 72 hours apart. In each UBT session, the baseline, 10-minute, and 15-minute (Delta15) gas samples were obtained to analyze excess (13)CO(2)/(12)CO(2) ratio (ECR). Histological stain and/or culture studies found that 33 of the patients with ESRD (47. 1%) and 42 of the control patients (60%) had H pylori infection. (13)C-UBT for H pylori detection in patients with ESRD was found to be only 93.8% sensitive and 85.3% specific. These results were achieved by gas sampling (Delta15) after HD therapy with a cutoff ECR value greater than 5. Conversely, the UBT in the control group achieved the greatest diagnostic efficacy (sensitivity, 97.6%; specificity, 96.4%) with a comparatively lower ECR cutoff value of 4. We conclude that the diagnostic accuracy for H pylori detection in patients with ESRD could be improved by performing (13)C-UBT (Delta15) after HD therapy and assessing the UBT with a cutoff ECR value greater than 5. However, the diagnostic efficacy of the UBT for patients with ESRD remained less accurate than that for dyspeptic patients without renal impairment.

Adolescent↗
PubMed1999

Distinct export pathway utilized by the hepatitis B virus posttranscriptional regulatory element.

The posttranscriptional regulatory element (PRE) of hepatitis B virus is an RNA element important for the export of viral mRNA from the nucleus to the cytoplasm. The cellular export pathway utilized by the PRE is controversial. We present data showing that PRE-dependent export is blocked by vesicular stomatitis virus matrix protein, an inhibitor of all cellular RNA export other than tRNA export. It is also blocked by a mutated form of Ran-binding protein 1, which blocks export mediated by the human immunodeficiency virus Rev and Rev-response element (RRE) but not export mediated by the simian retrovirus constitutive transport element (CTE). On the other hand, PRE-dependent export is not blocked by either TAgRex or leptomycin B, two agents that prevent Rev/RRE-mediated export. Therefore, PRE appears to utilize an export pathway different from that of Rev/RRE or CTE.

Biological Transport↗
PubMed1999

Granuloma annulare and human immunodeficiency virus infection.

OBJECTIVES: To characterize human immunodeficiency virus (HIV)-associated granuloma annulare (GA) by clinical, microscopic, and molecular methods and to investigate the role of Epstein-Barr virus infection in the pathogenesis of GA. DESIGN: Patients were evaluated clinically, and biopsy specimens of lesional skin were examined by light microscopy. Polymerase chain reaction and in situ hybridization for Epstein-Barr virus were performed on 4 and 12 biopsy specimens, respectively. SETTING: Academic referral center. PATIENTS: Thirty-four consecutive HIV-positive patients who have a clinical and histological diagnosis of GA. OUTCOME MEASURES: Clinical distribution of lesions, light-microscopic features, and the presence of Epstein-Barr virus DNA and RNA in biopsy specimens. RESULTS: Granuloma annulare was generalized in 20 patients and localized in 14. Twenty patients (59%) presented with acquired immunodeficiency syndrome. Unusual features were the presence of oral lesions in 1 patient, perforating lesions in 2 patients, and the coexistence of GA and Kaposi sarcoma in 1 biopsy specimen. Microscopic examination of 34 biopsy specimens showed a granulomatous pattern that was interstitial in 8, palisaded in 18, perforating in 2, and mixed interstitial and palisaded in 6. Special staining of all specimens was negative for organisms. Epstein-Barr virus infection was not detected by either polymerase chain reaction or in situ hybridization. CONCLUSIONS: Generalized GA is the most common clinical pattern in HIV infection. Granuloma annulare associated with HIV can present at all stages of HIV infection, but it is slightly more common in patients with acquired immunodeficiency syndrome. Epstein-Barr virus is an unlikely causative agent of HIV-associated GA. Granuloma annulare may be a manifestation of increasing immune dysregulation.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Activation of the grp78 and grp94 promoters by hepatitis C virus E2 envelope protein.

The hepatitis C virus E1 and E2 envelope proteins are targeted to the endoplasmic reticulum, but instead of being secreted, they are retained in a pre-Golgi compartment, at least partly in a misfolded state. Since secretory proteins which are retained in the endoplasmic reticulum frequently can activate the transcription of intraluminal chaperone proteins, we measured the effect of the E1 and E2 proteins on the promoters of two such chaperones, GRP78 (BiP) and GRP94. We found that E2 but not E1 protein activates these two promoters, as assayed by a reporter gene system. Furthermore, E2 but not E1 protein induces the synthesis of GRP78 from the endogenous cellular gene. We also found that E2 but not E1 protein expressed in mammalian cells is bound tightly to GRP78. This association may explain the ability of E2 protein to activate transcription, since GRP78 has been postulated to be a sensor of stress in the endoplasmic reticulum. Since overexpression of GRP78 has been shown to decrease the sensitivity of cells to killing by cytotoxic T lymphocytes and to increase tumorigenicity and resistance to antitumor drugs, this activity of E2 protein may be involved in the pathogenesis of hepatitis C virus-induced diseases.

Animals↗
PubMed1999

The effects of colchicine on a Peyronie's-like condition in an animal model.

PURPOSE: We have developed an animal model of Peyronie's disease by injecting transforming growth factor beta (TGF-beta) into the rat penis. Our objective is to study the effects of colchicine on the Peyronie's condition in an animal model. MATERIALS AND METHODS: Thirty-six adult male Sprague-Dawley rats received TGF-beta injections into the tunica albuginea and were divided into two groups (n = 18 each). Rats in the first group were divided into three subgroups (n = 6 each). Each rat in the three subgroups received the following: Subgroup 1 received colchicine, subgroup 2 received ibuprofen, and subgroup 3 received regular water. The rats were euthanized after 6 weeks. Rats in the second group were also divided into three subgroups. These rats received the same treatments as the rats in the first group, but treatments began 6 weeks after TGF-beta injection. These rats were euthanized after 12 weeks. Tunical tissue samples were collected and examined using Hart and trichrome stains, electron microscopy (EM), and western blot analysis for TGF-beta detection. RESULTS: In the first group, the colchicine-treated rats exhibited less collagen deposition and less elastic fiber fragmentation than the untreated or ibuprofen-treated rats. EM confirmed the results and showed normal distribution and shape of both collagen and elastic fibers in the colchicine-treated group. In the second group, the colchicine-treated rats exhibited less crowding of the collagen fibers. However, the elastic fibers remained fragmented and scarce. Western blot analysis showed significant down-regulation of TGF-beta expression (5/6) in the colchicine-treated group after 6 weeks. Down-regulation was observed in only 1/6 in both ibuprofen and non-treated groups. After 12 weeks 2/6, 1/6, and 1/6 rats displayed down regulation in the colchicine treated, ibuprofen treated, and non-treated groups, respectively. CONCLUSION: Early colchicine treatment may suppress a Peyronie's like condition in the rat animal model.

Animals↗
PubMed1998

Identification of glyceraldehyde-3-phosphate dehydrogenase as a cellular protein that binds to the hepatitis B virus posttranscriptional regulatory element.

The hepatitis B virus posttranscriptional regulatory element (PRE) is an RNA cis-element that is required for high-level expression of viral surface gene transcripts and appears to function by activating mRNA export to the cytoplasm. We have previously shown that multiple fragments of the PRE bind to two cellular proteins of approximately 35 and 55 kDa in molecular mass and that this binding correlates with function. By a combination of column chromatographic techniques and SDS-polyacrylamide gel electrophoresis, we have been able to purify the smaller protein. Amino-terminal sequencing of the purified protein shows identity to glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an RNA-binding glycolytic enzyme that has been implicated in the export of tRNA. Immunoprecipitation analysis reveals that GAPDH is indeed present in the protein-RNA complex resulting from incubation of crude nuclear extracts with a functional region of the PRE. Furthermore, binding of the cellular 35 kDa protein to the PRE fragment is blocked by NAPDH, as would be expected for RNA binding by GAPDH. Finally, purified commercial GAPDH also binds specifically to this RNA fragment. Therefore, GAPDH is one of the cellular proteins that binds to the PRE, and may be involved in the posttranscriptional regulation of hepatitis B virus gene expression.

Amino Acid Sequence↗
PubMed1998

Targeted disruption of the ubiquitous CNC-bZIP transcription factor, Nrf-1, results in anemia and embryonic lethality in mice.

The CNC-basic leucine zipper (CNC-bZIP) family is a subfamily of bZIP proteins identified from independent searches for factors that bind the AP-1-like cis-elements in the beta-globin locus control region. Three members, p45-Nf-e2, Nrf-1 and Nrf-2 have been identified in mammals. Expression of p45-Nf-e2 is largely restricted to hematopoietic cells while Nrf-1 and Nrf-2 are expressed in a wide range of tissues. To determine the function of Nrf-1, targeted disruption of the Nrf-1 gene was carried out. Homozygous Nrf-1 mutant mice are anemic due to a non-cell autonomous defect in definitive erythropoiesis and die in utero.

Amino Acid Sequence↗
PubMed1998

Histological and ultrastructural alterations in an animal model of Peyronie's disease.

OBJECTIVE: To determine the role of transforming growth factor beta (TGF-beta), one of the cytokines known to induce tissue fibrosis, in the induction of a Peyronie's-like condition, and to produce an animal model for the further study of Peyronie's disease. MATERIALS AND METHODS: Twenty-four adult male Sprague-Dawley rats were divided into two groups: in group 1, different concentrations of cytomodulin, a synthetic heptapeptide with TGF-beta-like activity, were injected into the tunica of each of 18 rats and six rats group 2 received saline injections as a control. The tunical tissues were taken after 3 days, 2 and 6 weeks and were examined histologically using Hart and trichrome stains. Electron microscopy was used to examine the ultrastructural changes in the same tissue samples. RESULTS: There were histological and ultrastructural alterations in 15 of 18 rats in group 1 (cytomodulin-injected), especially in tissue examined after 6 weeks. The most prominent histological changes were chronic inflammatory cellular infiltration, focal and diffuse elastosis, thickening, disorganization and clumping of the collagen bundles. The ultrastructural changes were in the form of densely packed collagen, fragmented and scarce elastic fibres, separation of neuronal fibres by interposing clumps of packed collagen, and perivascular collagen deposition as a part of the reorganization of the interstitial matrix. CONCLUSION: Cytomodulin can induce a Peyronie's-like condition in the rat penis, which may explain the role of TGF-beta in the pathogenesis of Peyronie's disease. With further refinement, such rats may be used as an experimental model for studies of Peyronie's disease.

Animals↗
PubMed1998

The effect of surgical trauma on rat tunica albuginea.

PURPOSE: Increased TGF-beta1 protein expression in tunica albuginea has been found to be associated with Peyronie's disease. The present study is designed to investigate whether surgical trauma induces TGF-beta up-regulation and histological changes in rat penis. MATERIALS AND METHODS: Thirty-two adult male Sprague-Dawley rats were divided into two groups. The first group (n=24) underwent incision and suture repair of the tunica albuginea of the penis. The second group (n=8) received sham surgery (incision of the penile skin and underlying fascia) as the control group. The trauma-induced group was divided into four subgroups in which the rats were euthanized at 6 hours (n=6), 1 day (n=6), 3 days (n=6), and 8 weeks (n=6). Two sham-operated (control) animals were also euthanized at each of the above time points. All tunical tissues from the trauma-induced and sham-operated rats were collected and examined histologically using Trichrome and Hart elastic fiber stain. Electron microscopy was used to study the ultrastructural changes of both trauma induced and control specimens. Western blotting technique was performed to study TGF-beta protein expression in both experimental and sham-operated groups. RESULTS: Tissue edema and hemorrhage between collagen bundles are noted in the experimental groups after 6 hours, 1 day and 3 days. At 8 weeks the most prominent changes observed were inflammatory cellular infiltration and disorganization of the collagen bundles. In the control group the tunica albuginea retains normal wavy regular appearance in all rats. This histological analysis is similar to the reported description of histological features of the acute phase of Peyronie's disease. Electron microscopy showed packed collagen bundles in the trauma-induced group with normal appearing elastic fibers. No abnormal change was detected in the control group. Immunoblot results revealed remarkable TGF-beta1 protein expression in 1, 5, 3, and 0 rats of trauma induced subgroups after 6 hours, 1 day, 3 days, and 8 weeks respectively. No TGF-beta1 protein expression in any rats in the control group was detected. No significant TGF-beta2 or TGF-beta3 protein expression was observed either in the trauma induced group or in the control group. CONCLUSION: Trauma can induce histological changes similar to the acute phase of Peyronie's disease but not the overt picture of the chronic phase of Peyronie's disease. It can also result in an early but transient up-regulation of TGF-beta1 protein expression in the rat penis. We conclude that surgical incisional trauma does not result in Peyronie's disease-like changes in the tunica.

Animals↗
PubMed1998

Expression of TGF-beta-1 mRNA and ultrastructural alterations in pharmacologically induced prolonged penile erection in a canine model.

PURPOSE: Transforming growth factor beta (TGF-beta) is known to induce fibrosis. Our objective was to study the role of TGF-beta as a possible mediator of fibrosis that may follow prolonged penile erection. MATERIALS AND METHODS: Prolonged penile erection was induced in seven adult male mongrel dogs by intracavernosal injection of papaverine into one of the corpora cavernosa while the other was used as a control. Intracavernosal pressure measurements were carried out prior to administration of papaverine and at the end of the procedure. Penile tissue was collected from anesthetized animals prior to euthanasia for histological and electron microscopic (EM) studies. RT-PCR was carried out for detection of mRNA on same tissue samples. RESULTS: The light microscopy showed stasis of blood in the cavernosal sinusoids. EM studies revealed sporadic endothelial defects, loss of plasma membrane integrity and cytoplasmic condensation. There was expression of TGF-beta1 mRNA in 66.7% of the experimental group compared with 16.7% of the control group. CONCLUSIONS: Pharmacologically induced low flow prolonged penile erection in canine models is associated with histomorphological changes in relatively short periods of time, suggesting that early therapeutic intervention is desirable. The gene expression for TGF-beta1 may be a mediator of fibrosis; therefore the use of anti-TGF-beta agents presents a possible tool for therapeutic intervention.

Animals↗